Identification of layers in optical coherence tomography of skin: comparative analysis of experimental and Monte Carlo simulated images.

BACKGROUND/PURPOSE: The goal of the study is comparative analysis of the layers in OCT images and the morphological structure of skin with thick and thin epidermis. METHODS: We analyzed the difference between skin with thin and thick epidermis in two ways. The first approach consisted in determination of the thicknesses of layers of skin with thin and thick epidermis of different localizations from experimental OCT images. The second approach was to develop numerical models fitting experimental OCT images based on Monte Carlo simulations revealing structure and optical parameters of layers of skin with thick and thin epidermis. RESULTS: The correspondence between the OCT images of skin with thin and thick epidermis and the morphological structure was confirmed. OCT images of healthy skin comprise three layers in case of skin with thin epidermis and four layers in skin with thick epidermis. The OCT image of the zone of the transition from skin with thick to skin with thin epidermis features five layers. CONCLUSION: The revealed differences in the structure of horny and cellular layers of epidermis, as well as of papillary and reticular dermis in skin with thin and thick epidermis specify different optical properties of these layers in OCT images.

Morphological changes in skin of different phototypes under the action of topical corticosteroid therapy and tacrolimus.

BACKGROUND/PURPOSE: The present study aimed to investigate the influence of topical corticosteroid therapy and tacrolimus on morphological indices of different skin phototypes and to optimize topical therapy using the OCT technique. METHODS: Twenty healthy volunteers aging from 20 to 30 (14 men and 6 women) took part in the study: 10 persons with skin phototype I, II and 10 persons with skin phototype V, VI. Morphological state of the skin was assessed before and during application of topical steroids of different strength and calciumneurin inhibitors for 49 days. Morphological state was studied in vivo using the optical coherence tomograph. RESULTS: Morphological manifestations of skin atrophy with the use of clobetasol propionate appear earlier than with the use of hydrocortisone 17-butyrate; this process was faster in representatives of groups V, VI. Epidermal thinning in the zone of tacrolimus application was not recorded in any phototype. CONCLUSION: Recording of early preclinical signs of epidermis thinning in the course of OCT follow-up may be an indication for changing the corticosteroid therapy by calciumneurin inhibitors, which will permit to individualize the therapy, to increase its efficacy, and to minimize the possibility of complications in each particular case.

Complex assessment of age-specific morphofunctional features of skin of different anatomic localizations.

OBJECTIVE: The goal of the described study was complex assessment of age-specific morphofunctional features of skin of different anatomic localization using optical coherence tomography (OCT). METHODS: Forty-three healthy volunteers aging from 4 to 74 years were enrolled in the study. Optical and functional skin parameters were studied in 18 areas of the human body. All the studied areas were classified as open and closed, depending on external impact. Structural parameters of skin were determined by means of the OCT device equipped with a removable, flexible probe with microscanner (registration certificate no. 022a2035/2213-05) designed and fabricated at the IAP RAS (Nizhny Novgorod, Russia) with longitudinal and transverse resolution of about 20 µm. RESULTS: Age-specific morphofunctional features of skin most evident in areas exposed to external action were found. Statistically significant difference in elasticity (-0.57, P = 0.00012) in areas closed to external action (further referred to as closed areas) and in useful signal depth, hydration and elasticity in areas exposed to external action (further referred to as open areas) was assessed for different age groups. Analysis of the dependence of parameters on age showed statistically significant correlations between age and thickness of cellular layers of the epidermis (-0.33, P = 0.035), pigmentation level (-0.22, P = 0.044) and elasticity in closed areas and highly significant correlations between age and hydration and elasticity in open areas. CONCLUSION: The current work is concerned with investigation of age-specific morpho-functional parameters of skin of different localizations.

Contrasting properties of gold nanoparticles for optical coherence tomography: phantom, in vivo studies and Monte Carlo simulation.

The possibility of using silica-gold nanoshells with 150 nm silica core size and 25 nm thick gold shell as contrasting agents for optical coherence tomography (OCT) is analyzed. Experiments on agar biotissue phantoms showed that the penetration of nanoshells into the phantoms increases the intensity of the optical coherence tomography (OCT) signal and the brightness of the corresponding areas of the OCT image. In vivo experiments on rabbit skin demonstrated that the application of nanoshells onto the skin provides significant contrasting of the borders between the areas containing nanoshells and those without. This effect of nanoshells on skin in vivo is manifested by the increase in intensity of the OCT signal in superficial parts of the skin, boundary contrast between superficial and deep dermis and contrast of hair follicles and glands. The presence of nanoshells in the skin was confirmed by electron microscopy. Monte Carlo simulations of OCT images confirmed the possibility of contrasting skin-layer borders and structures by the application of gold nanoshells. The Monte Carlo simulations were performed for two skin models and exhibit effects of nanoparticles similar to those obtained in the experimental part of the study, thus proving that the effects originate exactly from the presence of nanoparticles.